Paper Pulp Tank Explosion
In a paper plant, an explosion occurs in a paper pulp tank while 2 workers were carrying out pipes cutting with a grinder on the roof of the tank. Detailed analysis of the event was performed by two independent experts. The paper pulp stored under certain conditions can ferment and produce hydrogen.The final expert report establishes the explosion process as follows:- the pulp stored in the tank has released hydrogen at a rate such that the LFL (lower flammability limit) could be reached within a few hours,- hydrogen mixed with the air in the tank top to form an ATEX,- the ignition source of ATEX is an incandescent particle produced during cutting with grinder of the pipe connected to the upper gaseous part of the tank,- the overpressure developed by the explosion led to the rupture of the tower roof at the level of the connection welding with the cylindrical flange.It is likely that this ATEX was not permanently present in the tank top and that it depends on particularly variations in its filling rate. On the day of the explosion, all ATEX explosion conditions(formation and inflammation) were present, which was not the case during previous hot spot work where the filling rate of the tank was significantly lower.ARIA 39635
Event Date
January 18, 2011
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
Immediate cause of the event was the formation of hydrogen from pulp fermentation and its ignition due to cutting work during maintenance. Root cause is failure to identify the possible formation of ATEX atmosphere.It is likely that this ATEX was not permanently present in the tower's sky and that it depends inparticularly from variations in its fill rate. On the day of the explosion, all explosion conditions of the ATEX (formation and ignition) were combined, which was not the case in previous hot spot work where the tower's fill rate was significantly lower.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
pulp storage
Storage/Process Medium
Location Type
Location description
Industrial Area
Pre-event Summary
Maintenance works where being performed, which contributed to the severity of the consequences.
Currency
Lessons Learned
Lessons Learned
This accident shows that pulp obtained from papers and cartoons without chemical processing can become the site of a microbiological activity. This phenomenon produces hydrogen which can form an explosive atmosphere in the storage tank under specific conditions (high filling level, agitation of the pulp after a long period of stop) In this type of paper manufacturing plants the risk of an explosion has to be taken into account in the safety design and the operational risk analysis. Among the possible measures there are training the staff in hydrogen safety, performing control with a hydrogen sniffer before maintenance, and considering a new ATEX zoning including top of paper pulp tank. .
Event Nature
Emergency Action
Employees, including first-aid workers, heard the sound of the explosion and went to the site totake care of the victim, who was conscious but cannot move.Rescue services, including a SAMU doctor, entered in action and the injured person was flown by helicopter to a hospital, where he died of his injuries early in the evening.The use of the FL storage tower was immediately prohibited by inspection of classified facilities. This decision led to the cessation of production, as the tank was essential to the operation of the plant.
Release Type
Release Substance
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
ARIA event no 39635